Antioxidants in gasoline fuels



I 3,031,281 ANTIOXIDANTS IN GASOLINE-FUELS Ronald B. Spacht, Kent, Ohio, assiguor to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation,

This invention relates to the preservation of oxidizable compositions such as rubbers and gasoline and, more particularly, to the provision and use of a new class of phenothiazoxy compounds which are useful as age resistors for the various oxidizable rubbers and gasoline.

.Unsaturated materials such as rubbers and gasoline are subject to deterioration from many sources, such as sunlight, ozone, atmospheric oxygen, .the presence of heavy metals, etc. Both cured and uncured natural and synthetic elastomers are subject to such deterioration. Deterioration in cured stocks of rubber may vary with the type of stock, the state of cure and'the amount of surface exposed. Also, the temperature of the oxidizable compositions is an important factor in deterioration. An ideal antioxidant would be one which would protect the oxidizable compound from deterioration regardless of time, physical state of the oxidizable compound, and regardless of use. Since no such general antioxidant has been discovered, compromises must be made in the selection of an antioxidant for a particular use. i

It is an object of the present invention to provide an antioxidant composition which is capable of protecting various oxidizable rubbers and gasoline for extended periods of time. It is another object of this invention to provide a phenothiazoxy compound which is capable of protecting various oxidizable rubbers and gasoline from deterioration from oxygen, ozone, and/ or sunlight.

In the practice of the present invention, various oxidizable compositions are protected from deterioration by means of phenothiazoxy esters. These compounds may be made according to customary chemical'practices. For example, the acids can be made by heating compounds of the general structure wherein R is H or an alkyl radical having 1 to 4 carbons and x is 1 to 4 with sulfur in the presence of a catalyst such as iodine at a temperature ranging from 150 to 200 C. The corresponding esters are made by first forming the esters of the parent acids and then treating these esters with sulfur at a temperature between 150 and 200 C. in the presence of I or similar catalysts.

The pheonthiazoxy esters of this invention can be described as phenothiazoxy compounds conforming to the following structure:

wherein R is selected from alkyl radicals containing from 1 to 9 carbon atoms, R is selected from the group consisting of hydrogen and alkyl radicals having from 1 to 4 carbon atoms and wherein x is an integer of from 1 to 4.

Representative phenothiazoxy esters which are useful me Me 3,031,281 -Patented Apr. 24, 1962 in the, practice of this invention are the methyl, ethyl, propyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, octyl, isooctyl and nonyl esters of the above described acids. f

The invention can be further illustrated by means of the following examples which are not intended as limitations on the scope of the invention.

EXAMPLE 1 by means of methanol to yield. crystals having a melting point of 107 C. Proof of the product obtained wasby means of nitrogen and sulfur analysis. The nitrogen content was 4.33% as compared with a calculated percent of 4.25 and the sulfur content was 10.52 as compared with a calculated percent of 9.73.

The compound of Example 1 was tested as an antioxidant in extracted pale crepe gum stock vulcanizates, in a natural rubber tread stock, and in uninhibited catalytically cracked gasoline. The following formulation was used for extracted pale crepe vulcanizates:

Extracted pale crepe 100.0 Zinc oxide 5.0 Sulfur 3.0 Hexamethylenetetrannne 1.0 Stearic acid 1.5 Antioxidant 1.0

Table I Orig. Percent Percent Material Tensile Final TR Wt. Inc.

Butyl-pbenothiazoxy acetate 2, 150 2, 350 109. 5 0. 29 Butylated-p-eresol 2, 000 1, 670 83. 6 0.16 No antioxidant 0 0 0 18.00

The antioxidant of Example 1 was incorporated into the following natural rubber vulcanizate:

TREAD STOCK FORMULATION Samples were cured for 70 minutes at 260 F. and thereafter aged in an air bomb for 8 hours at 114 C. and pounds per square inch pressure, giving the following results:

The antioxidant prepared according to Example 1 was tested as an antioxidant for gasoline according to ASTM standard test D525 known as the induction period test. A sample of uninhibited catalytically cracked gasoline was used as a base for the induction period test.

Table 111 Gone Induction Antioxidant g./l. Period,

Minutes Butyl-phenothiazoxy acetate 0. 025 607 Phenyl-fl-Naphth ylamine 0. 025 238 Control-n antioxidant... 0. 025 193 Butylated-p-cresol 0. 025 346 The above information illustrates the efficacy of phenothiazoxy compounds as antioxidants for oxidizable compositions such as rubbers and gasoline. Although this invention has been described by reference to pure compounds, mixtures of the several phenothiazoxy esters can be used inthe practice of the invention.

The rubbers which can be protected by the products of this invention are the oxidizable rubbery polymers of conjugated dienes which include natural rubber and the various synthetic diene rubbers which are similar to natural rubber in their aging characteristics, such as polychloroprene; butyl rubber, which is a polymerization product of a major proportion of a mono olefin, such as isobutylene, and a minor proportion of a multi olefin, such as butadiene or isoprene; the rubbery copolymers of butadiene and styrene which may contain from 50 to 75% by weight of butadiene; the rubbery copolymers of butadiene and acrylonitrile and polyisoprene.

The products of the invention are useful as age resistors for raw rubbers in latex form, coagulated rubber latices or vulcanized rubbers, and may be present in an amount of from 0.25 to 5.0% by weight, based on the weight of the rubber, although it is generally preferred to use from 0.5 to 2.0% by weight, based on the weight of rubber.

The antioxidants of this invention can be incorporated into rubber in any customary manner. They may be added in the form of physical mixtures or in the form of emulsions using any of the known emulsifiers such as monovalent metal hydroxides, fatty acids, organic soaps, etc. They may be added to the rubber in the form of latex, or they may be milled into coagulated rubber in the usual manner.

The various highly refined hydrocarbons which can be protected by the products of this invention can be described as catalytically cracked, thermally cracked gasoline or blends thereof. Higher boiling fractions such as kerosene, fuel oil, and diesel oils are also included within the scope of this invention.

The compounds of this invention can be used to stabilize the highly refined hydrocarbons by adding about 001% to 0.1% by weight of the antioxidant to the highly refined hydrocarbons.

This application is a division of Serial No. 693,544 filed on October 31, 1957, and now abandoned.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. A refined gasoline containing as an antioxidant in an antioxidant amount a phenothiazoxy ester conforming to the following general formula wherein R is selected from the group consisting of hydrogen and alkyl radicals having from 1 to 4 carbon atoms, x is an integer of from 1 to 4 and wherein R is an alkyl radical containing from 1 to 9 carbon atoms. 2. A refined gasoline containing as an antioxidant in an antioxidant amount a mixture of phenothiazoxy esters conforming tothe following general formula wherein R .is selected from the group consisting of hydrogen and alkyl radicals having from 1 to 4 carbon atoms, x is an integer of from 1 to 4 and wherein R is an alkyl radical containing from 1 to 9 carbon atoms. 3. A refined gasoline containing as an antioxidant in an antioxidant amount, butyl phenothiazoxy acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,006,756 Bartram July 2, 1935 2,587,662 Smith Mar. 4, 1952 2,781,318 Cyphers Feb. 12, 1957 OTHER REFERENCES Baltzly et al.: J. Am. Chem. Soc., vol. 68, pp. 2673- 2678 (1946).

Mode of Action of Phenothiazine-Type Antioxidants, by Murphy et al., Ind. and Eng. Chem, pp. 2479-2487, December 1950.

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 3,031,281 April 24, 1962 Ronald B. Spacht It is hereby certified that error appears in the above numbered petent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, lines 23 to 27, and lines 35 to 38, the formulas,

each occurrence, should appear as shown below instead of as in the patent:

RI R! Signed and sealed this 18th day of September 1962.,

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

1. A REFINED GASOLINE CONTAINING AS AN ANTIOXIDANT IN AN ANTIOXIDANT AMOUNT OF PHENOTHIAZOXY ESTER CONFORMING THE FOLLOWING GENERAL FORMULA 